1. Field of the Invention
The present invention relates to a drive apparatus for moving an object (driven object) in a desired direction, and an XY drive apparatus on which said drive apparatus is equipped.
2. Description of the Prior Art
An example of the prior art having this type of drive apparatus is the XY drive apparatus shown in FIG. 1.
As shown in FIG. 1, said XY drive apparatus is composed of X table 1; installed on the floor or a mounting frame and so forth in a workshop, and Y table 2 arranged to cross said X table 1 and move while being supported by said X table. Furthermore, since X table 1 and Y table 2 are mutually of nearly the same constitution, the following provides a detailed description of X table 1 only, while an explanation of Y table 2 is omitted. However, those constituent members of Y table 2 that correspond to the constituent members of X table 1 are indicated using the same reference numerals.
As indicated in FIGS. 1 and 2, X table 1 has a long, roughly rectangular plate-shaped base 13, and side plates 14 provided on both sides of said base 13. Mounting member 15 is attached to one end of base 13, and motor 16 and sensor connector 17 are mounted to the mounting member 15. In addition, fixed bearing mechanism 18 is provided on the other end of base 13, and feed mechanism 19 is supported by the fixed bearing mechanism 18. In addition, the torque of motor 16 is transmitted to feed mechanism 19 through coupling 20. Furthermore, as is commonly known, feed mechanism 19 is composed of screw shaft 21 and nut 22 which moves by the rotation of this screw shaft 21 by screwing onto said screw shaft 21.
As shown in FIG. 2, one end of screw shaft 21 is axially supported to as to rotate freely by bearing 18a equipped in fixed bearing mechanism 18, while the other end 21a is formed narrower than the screw portion and is axially supported so as to rotate freely by bearings 23a equipped in bearing unit 23. In addition, the gap between this other end 21a and bearings 23a in the axial direction can be eliminated by tightening lock nut 24, thus restricting the movement of screw shaft 21. This constitution is also such that the torque of motor 16 is transmitted by being coupled to coupling 20.
On the other hand, as shown in FIG. 3, nut 22 is fastened to the end of moving table 27 having a roughly T-shaped cross-section by a plurality of bolts 22a. This moving table 27 is formed to a size that is contained within the width of side plates 14, and two table projections 27a are formed in parallel on the upper end surfaces of side plates 14 on the upper surfaces of its left and right sides. The previously described Y table 2 is attached to these table projections 27a by bolts (not shown). Furthermore, as shown in FIGS. 1 and 3, cover 28 is arranged so as to be positioned to the inside of both of these table projections 27a, preventing the entrance of dust and so forth. In addition, as shown in FIG. 3, stopper 29, having a prescribed length, protrudes from one end surface of moving table 27. This stopper 29 is for restricting the movement of moving table 27 at the end position of axial movement of said moving table 27.
As shown in FIGS. 2 and 3, moving table 27 is supported by a pair of sliders 31. These sliders 31 are formed to have roughly U-shaped cross-sections, and slide along track rails 32 mounted on mounting surfaces 13a of base 13. A guiding device which guides moving table 27 in the direction (X) it is to move is composed by these sliders 31 and track rails 32. Furthermore, two grooves 13b are formed parallel to the above-mentioned mounting surfaces 13a in base 13, and sensors 34 are mounted at prescribed locations in both of the grooves 13b for detecting the stroke limit and origin position of moving table 27.
Next, the following provides an explanation of the operation of the XY drive apparatus composed in the manner described above.
To begin with, electrical power is supplied to motors 16 of X table 1 and Y table 2.
Next, when a power voltage is applied to motor 16 of X table 1, the motor 16 turns and torque is transmitted to screw shaft 21 of feed mechanism 19 through coupling 20. As a result of rotation of this screw shaft 21, moving table 27 to which nut 22 is attached moves linearly in the X direction along track rails 32. Consequently, Y table 2 mounted on said moving table 27 also moves in the X direction.
On the other hand, since Y table 2 is composed so that moving table 27 with which it is equipped (see FIG. 1) independently moves linearly in the Y direction in the same manner as the above-mentioned X table 1, by controlling the operation of said X table 1 and Y table 2 using a control circuit not shown, an electronic component and so forth on which work is to be performed on moving table 27 of Y table 2 can be moved two-dimensionally as desired.
As has been described above, in the drive apparatus of the prior art, a driven object in the form of moving table 27 is driven by a feed mechanism 19. However, the occurrence of deflection in nut 22 within the plane perpendicular to the axial center of screw shaft 21, namely the radial direction, accompanying rotation of said screw shaft 21 cannot be avoided due to curvature and center misalignment of screw shaft 21 and mounting errors and so forth in feed mechanism 19. Thus, the drive apparatus of the prior art exhibits radial deflection, pitching or yawing of electronic components and so forth on moving table 27 caused by deflection of nut 22, thereby having a detrimental effect accuracy of the location or positioning of the electronic components and so forth.
In addition, since there have recently been trends to attempt to simplify the construction of the above-mentioned drive apparatus and XY drive apparatus to reduce the size of said apparatuses as well as reduce the number of parts, a solution to these problems is needed.